Rubber vulcanization



United States Patent RUBBER VULCANIZATION Roland H. Goshorn, Trenton, and William W. Levis, Jr., Wyandotte, Mich., assignors, by mesne assignments, to The Pennsylvania Salt Manufacturing Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application February 11, 1952, Serial No. 271,072

14 Claims. (Cl. 260-795) The present invention pertains broadly to a novel series of rubber vulcanization accelerators, many of which are of the delayed action type. More specifically, it pertains to methods of vulcanization using these accelerators, and to rubber compositions containing said accelerators.

The new compounds and methods of preparing them are claimed in our co-pending application Serial No. 258,502, filed November 27, 1951, of which the present application is a continuation-in-part. Said co-pending application has now been abandoned in favor of our co-pending application Serial No. 279,246, filed March 28, 1952, now U. S. Patent No. 2,685,588.

The structure of these new compounds, and their preparation from N-substituted thiocarbamyl halides and mercaptides of l.3,4-thiadiazole-2,S-dithiol, is illustrated as follows:

wherein M represents a monovalent metal or metalloid cation such as an alkali metal or ammonium; wherein X represents a halogen; wherein R1, taken individually, represents one of the group consisting of alkyl, aralkyl, aryl, alkaryl, cycloalkyl, alkyl-substituted cycloalkyl, furfuryl, and tetrahydrofurfuryl radicals; wherein R2, taken individually, represents one of the group consisting of alkyl, aralkyl, cycloalkyl, alkyl-substituted cycloalkyl, furfuryl, and tetrahydrofurfuryl radicals; and wherein R1 and R2, taken collectively, represent one of the group consisting of polymethylene and oxapolymethylene radicals.

The foregoing equation illustrates the formation of diesters of 1,3,4-thiadiazole-2,5-dithio1, but it is to be understood that monoesters may likewise be formed by employing an equimolar ratio of reactants, instead of two moles of N-substituted thiocarbamyl halide per mole of dimercaptide as in the formation of diesters. At times such monoesters may be formed as valuable by-products during the preparation of the diesters, and may be advantageously recovered from the reaction mixtures.

The monoesters are, of course, monomercaptides and such monomercaptides may be converted to monomercaptan-monoesters by treatment with a suitable acid, e. g., hydrochloric acid or sulfuric acid.

If desired, the monomercaptide-monoesters may be 2 further reacted with any N-substituted thiocarbamyl halide employed herein, a diester being thus obtained.

The products of the invention, including the diesters, the monomercaptide-monoesters, and the monomercaptan-monoesters, may be represented by the general formula group consisting of hydrogen, alkali metals, ammonium, and the radical in which radical R1 and R2 have the same meanings as above.

The diester products contain two N-substituted thiocarbamyl radicals, which it will be understood may be the same or different. It will likewise be understood that R1 and R2, when taken individually, may be the same or different in any N-substituted thiocarbamyl radicals which are twice substituted on nitrogen by univalent radicals of the aforesaid kind; this applies both to the products of the invention and to the halide reactants.

Examples of alkali metals are sodium and potassium. Examples of halogens are chlorine, bromine, and iodine.

Examples of alkyl radicals are those containing from 1 to 18 carbon atoms such as methyl, ethyl, propyl, butyl, amyl, etc., and proceeding through octadecyl and higher, and including isomeric forms thereof. Examples of aralkyl radicals are benzyl, phenylethyl and phenylpropyl. Examples of aryl radicals are phenyl, alpha-naphthyl, and beta-naphthyl. Examples of alkaryl radicals are tolyl, xylyl, trimethylphenyl, ethylphenyl, propylphenyl, butylphenyl, methylbutylphenyl, dimethylethylphenyl, methylnaphthyl, butylnaphthyl, diand trimethylnaphthyl, and ethylbutylnaphthyl, including isomeric forms thereof. Examples of cycloalkyl radicals are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and decahydronaphthyl. Examples of alkyl-substituted cycloalkyl radicals are methylcyclohexyl, dimethylcyclohexyl, et'hylcyclohexyl, amylcyclohexyl, hexylcyclohexyl, methylcyclobutyl, methylcyclopentyl, methylcycloheptyl, and methylcyclooctyl, including isomeric forms thereof.

When R1 and R2 are taken collectively, examples of such radicals are tetramethylene, pentamethylene, hexamethylene, and 3-oxapentamethylene.

The N-substituted thiocarbamyl halides which may be employed in the reaction include those in which the nitrogen atom is twice substituted by similar alkyl radicals, e. g. dimethyl-, diethyl-, dipropyl-, dibutyl-, diamyl-, dihexyl-, diheptyl-, dioctylthiocarbamyl chlorides, etc.; or by two dissimilar alkyl radicals, e. g. methyl-ethyl-, ethyl-propyl-, methyl-propyl-, methyl-octadecylthiocarbamyl chlorides, etc.; or by a single polymethylene radical, e. g. tetramethylene-, pentamethylene-, hexamethylenethiocarbamyl chlorides, etc.; or by a single oxapolymethylene radical, e. g. 3-oxapentamethylenethiocarbamyl chloride, etc.; or by one aryl and one alkyl radical, e. g. phenyl-methyl-, phenyl-ethy1, phenyl-propyl-, naphthylmethylthiocarbamyl chlorides, etc; or by one alkyl and one alkaryl radical, e. g. methyl-tolyl-, ethyl-toly-l, propyl-tolyl-, methyl-xylyl-, ethyl-xylyl-, propyl-xylylthiocarbamyl chlorides, etc.', or by one alkyl and one aralkyl radical, e. g. methyl-benzyh, ethyl-benzyl-, propyl-benzyl-, methyl-phenylethyl-, ethyl-phenylethyl-, propyl-phenylethylthiocarbamyl chlorides, etc.; or by one aryl and one aralkyl radical, e. g. phenyl-benzyl-, phcnyl-phenylethylthiocarbamyl chlorides, etc; or by two aralkyl radicals, e. g. dibenzyl-, benzyl-phenylethyl-, diphenylethylt-hiocarbamyl chlorides, etc.; or by one alkyl and one cycloalkyl radical, e. g. methyl-cyclohexyl-, ethyl-cyclohexyl-, amyl-cyclohexyl-, methyl-cyclopropylthiocarbamyl chlorides, etc; or by one alkyl and one alkyl-substitut'ed' cycloalkyl radical, e. g. methyl-methylcyclohexyl-, ethylamylcyclohexy1-, propyl methylcyclobutylthiocarbamyl chlorides, etc; or by one aralkyl and one cycloalkyl radical, e. g. benzyl-cyclohexyl-, phenylethylcyclohexylthiocarbamyl chlorides, etc; or by one. aryl and one cycloalkyl radical, e. g. phenyl-cycl'ohexyl-, phenyl-cyclopentyl-, naphthyl-cyclohexylthiocarbamyl chlorides, etc.; or by one aryl and one alkyl-substituted cycloalkyl radical, e. g. phenyl-dirnethylcyclohexyl-, naphthyl-cthylcyclohexylt-hiocarbamyl chlorides, etc; or by one alkaryl and one aralkyl radical, e. g. tolyl-benZyl-, xylyl-benzyl-, methylnaphthyl-benzyl-, tolyl phenylethylthiocarbamyl chlorides, etc; or by one alkaryl and one cycloalkyl radical, e. g. xylyl-cyclohexyh, tolyl-cyclobutyl-, amylnaphthyl-cyclohexylthiocarbamyl chlorides, etc.; or by one alkaryl and one alkyl-substituted cycloalkyl radical, e. g. tolyl-dimethylcyclohexyl-, methyl-naphthyl-rnethylcyclohexylthiocarbamyl chlorides, etc; or by two cycloalkyl radicals, e. g. dicyclopropyl-, dicyclohexyl-, cyclobutyl-cyclopentylthiocarbamyl chlorides, etc; or by one cycloalkyl and one alkyl-substituted cycloalkyl radical, e. g. cyclohexyl-rnethylcyclohexyl-, cyclopropyl-methylcyclobutylthiocarbamyl chlorides, etc.; or by two alkylsubstituted cycloalkyl radicals, e. g. bis(methylcyclohexyl) methylcyclobutyl amylcyclohexylthiocarbamyl chlorides, etc.; or by two similar or dissimilar furfuryl or tetrahydrofurfuryl radicals, e. g. difurfuryl-, furfuryltetrahydrofurfuryl-, and bis(tetrahydrofurfuryl)thiocarbamyl chlorides; or by two dissimilar radicals, e. g. methyl-furfuryl-, amyl-furfuryl-,

ylethyl-tetrahydrofurfuryl phenyl-furfuryl-, naphth-yltetrahydrofurfuryl-, xylyl-furfuryl-, tolyl-tetrahydrofurfuryl-, cyclohexyl-furfuryl-, cyclohexyl-tetrahydrofurfuryl-, amylcyclohexyl-furfuryl-, methylcyclohexyl-tetrahydrofurfurylthiocarbamyl chlorides, etc.

Preferably the number of carbon atoms per hydrocarbon radical attached to the nitrogen atom of the N-substituted thiocarbamyl halide does not exceed 8, and more particularly does not exceed 6. Of particular interest are those compounds in which carbamate nitrogen is substituted by a pentamethylene radical or by two identical alkyl radicals containing from 1 to 8 carbon atoms in each alkyl radical.

In conducting the reaction, the reactants are brought together and reacted preferably in the presence of a solvent or liquid diluent which is non-reactive in the prevailing environment. The mercaptide may be introduced into the N-substituted thiocar-bamyl halide or alternatively the latter may be introduced into the former. In general, however, it is preferred to introduce the N- substituted thiocarbamyl halide which may be in the form of a finely divided solid, a liquid, a solution, or a suspension, into an aqueous solution of the mercaptide.

Any desired concentration of said aqueous mercaptide solution may be employed, such as up to the saturation concentration at the prevailing temperature, and in certain instances it may even be desirable to have some of the mercaptide present in solid form. A 20% solution, for example, is very satisfactory when the sodium di-v mercaptide is being reacted.

ethyl-tetrahyd-rofur furyl-, benzyl-methylcyclohexyl-, benzyl-furfuryl-, phen-- The N-substituted thiocarbamyl halide may be added to the aqueous solution or suspension of the mercaptide in the form of a finely divided solid, but more preferably as a liquid, for example, as molten material (in the case of normally solid halides), or in the form of a solution. The particular solvent employed is not highly critical providing it be substantially inert in the reaction environment. Likewise, the amount employed may vary widely, although it may often be desirable to employ s-uflicient solvent to maintain the halide in liquid phase. Suitable solvents, for example, include hydrocarbons such as hexane, petroleum naphtha, benzene, toluene, etc., and chlorinated hydrocarbons, such as carbon tetrachloride, chlorobenzene, etc.v

It will he understood, of course, that the melting points of the'N-substituted thiocarbamyl halides coming within the scope. of this invention. will differ widely; in fact,

many are liquids. at temperatures: well below those contemplated for the. preferred conduct of the process. In such event, the non-reacting liquid, if, employed, will function primarily as. a diluent for the halide, and possibly also as a solvent for the product.

Regardless of the order of addition of the reactants or of the particular physical form of the reactants prior to mixing, it is highly desirable that the reaction mixture be subjected to agitation during the progress of the reaction.

Reaction usually occurs readily at room temperature, reaction temperatures below 100 C. being preferred, such as between 0 C. and 100 C., and more particularly between 20 C. and 80 C. Lower temperatures may be used, but usually are attended by a reduced velocity of reaction and a reduced fluidity of the reaction mixture. Higher temperatures may be employed, but consideration should be given to the thermal stability of the N-substituted thiocarba myl halide being reacted, as well as of the desired reaction product.

The reaction may be carried out at any desired pressure, such as atmospheric, sub-atmospheric, or superatmospheric, atmospheric pressure being very suitable. Also the reaction may be carried out in batch, semicontinuously, or continuously as desired.

The organic products of the reaction may be readily purified and may be shown by chemical analysis to cor.- respond closely in empirical formula to the respective expected and desired products.

The dimercaptide starting materials may be derived from any source known in the art, Likewise, the N- substituted thiocarbamyl halides may be prepared by any means known in the art, such as by the process described and claimed in U. S. Patent 2,466,276.

Substituted thiocarbamyl chlorides are frequently obtained admixed with free sulfur. If desired, the chlorides may be separated from the sulfur before said chlorides are employed as reactants in the present invention. Alternatively, however, such admixtures may be employed for reaction purposes without separation, the sulfur be ing inert toward the reactants and the desired products. In such event, the products will of course contain sulfur as-an impurity; if desired, the sulfur may be readily separated. from said products.

The following examples illustrate the preparation of the new accelerators, and while aqueous media are. employed, it is. to be understood that this is not a necessary condition, for if desired any other solvent or diluent, particularly if non-reactive in the prevailing environment, may be employed, examples of which are hydrocarbon solvents, aliphatic or aromatic, such as benzene, toluene, hexane, etc, and chlorinated hydrocarbon solvents, aliphatic or aromatic, such as carbon tetrachloride, chlorobenzene, etc.

EXAMPLE 1 A I-liter Erlenmeyer flask equipped with stirrer, thermometer, and gas inlet tube was charged with 592 g. (2.0 moles) 9f molten, anhydrous tetraethylthiuram disulfide. This liquid was stirred vigorously and chlorine was passed in rapidly, the temperature of the reaction mixture being maintained between 65 C. and 70 C. A total of 142 g. (2.0 moles) of chlorine was added in 30 minutes. The resulting reaction mixture comprised diethylthiocarbamyl chloride and sulfur. Chlorination was discontinued, and the mixture was heated to about 105 C. and stirred until all the free sulfur had dissolved in the diethylthiocarbamyl chloride. This required approximately 30 minutes.

A aqueous solution of 1,3,4-thiadiazolyl-2,5-- disodium mercaptide containing 2.0 moles of this product was transferred to a 2-gallon glass vessel equipped with thermometer, electrically heated dropping funnel, and high speed stirrer. The stirrer comprised a stainless steel shaft, at one end of which was a disk 1 inch in diameter and having 16 pitched saw teeth giving downward circulation; this stirrer was driven by a high speed electric motor (7500 R. P. M.)

Stirring was commenced, and the above chloride-sulfur solution, maintained at about 100 C. in the dropping funnel, was slowly added to the mercaptide solution in 45 minutes; occasional cooling was resorted to in order to maintain the reaction mixture between C. to C.

Water (500 g.) was added to improve the fluidity of the resulting thick slurry. Stirring was continued for minutes, at which time 552 g. of 28.2% aqueous solution of sodium sulfide (2.0 moles of the sulfide) was added to the mixture to solubilize the free sulfur, and stirring was continued for another hour.

The mixture was then filtered, and the solid product was thoroughly washed with water and dried at C. The 1,3,4 thiadiazolyl 2,5-bis(diethyldithiocarbamate) thus obtained was a light tan powder, melting at 93.5- 95 C., and weighing 655 g. (85% yield).

A sample of 1,3,4-thiadiazolyl-2,5-bis(diethyldithiocarbamate) was recrystallized once from methyl alcohol and once from acetonitrile. The resulting pure compound melted at 9596 C. Calculated for C12H2oN4Ss: C, 37.86; H, 5.30; N, 14.72; S, 42.12. Found: C, 38.00, 37.35; H, 5.38, 5.33; N, 14.65, 14.73; S, 42.17, 42.35.

EXAMPLE 2 The chlorination apparatus and general procedure of the preceding example were used to react 408 g. (1.0 mole) of tetra-n-butylthiuram disulfide, M. P. 31.5- 33.5 C., with 71 g. (1.0 mole) of chlorine in 25 minutes,

the temperature of the reaction mixture being maintained between 45 C. and 50 C. Chlorination Was discontinned, and the mixture was stirred and heated to between 105 C. and 110 C. for 20 minutes. There was thus provided a solution of sulfur in di-n-butylthiocarbamyl chloride.

An aqueous solution of 1,3,4-thiadiazolyl-2,S-disodium mercaptide weighing 1348 g. and containing 1.0 mole of this compound was reacted with the above sulfur-containing di-n-butylthiocarbamyl chloride, using the same apparatus and general procedure described in the preceding example. Addition of the chloride-sulfur solution was completed in 30 minutes, during which time the temperature of the reaction m xture was maintained between 35 C. and 40 C.

Stirring was continued for 30 minutes. An aqueous solution weighing 340 g. and containing 1.5 moles of sodium sulfide was added, the mixture was stirred at about 30 C. for 1 hour, filtered, washed with water, and dried at 40-45 C. The resulting 1,3,4-thiadiazolyl-2,5 bis(di-n-butyldithiocarbamate) was a light tan powder, M. P. 72.576.5 C. The yield was 458 g. (93.3%).

A sample of 1,3,4-thiadiazolyl-2,5-bis(di-n-butyldithiocarbamate) was recrystallized from acetonitrile to a constant melting point of 77.5-78 C. Calculated for CaoHssNgSx N, 11.37. Found: N, 11.45, 11.56.

6 EXAMPLE 3 1.0 mole of 1,3,4-thiadiazolyl-2,S-disodiurri mercaptide (contained in 960 g. of aqueous solution) was charged into a l-gallon glass vessel provided with thermometer, electrically heated dropping funnel, and high speed stirrer. Dimethylthiocarbamyl chloride (247 g. or 2.0 moles) was placed in the funnel and maintained in molten condition; this chloride had been distilled and contained substantially no free sulfur. Addition of the chloride to the mercaptide solution was carried out in 30 minutes, with stirring, the reaction mixture being maintained between 30 C. and 40 C.

Water (200 g.) was added to the resulting thick slurry, stirring was continued for 15 minutes, 20 g. of 20% sodium hydroxide solution was added, and the mixture was stirred 15 minutes more.

The solid product was recovered by filtration, washed with water, and dried at 60 C. There was thus obtained 275 g. yield) of a powder, ivory in color, and having a melting point of 181-185 C. with decomposition.

The product was found to be relatively insoluble in such common solvents as methyl alcohol, acetone, and benzene. However, it was soluble in hot dimethy1formamide, and it was recrystallized from that solvent, recovered by filtration, washed with acetone, and dried at 80 C. M. P. 193-1945 C. with decomposition. Calculated for CsH12N4S5: N, 17.27. Found: N, 17.33, 17.38.

' EXAMPLE 4 Diisobutylthiocarbamyl chloride was prepared by reacting 408 g. (1.0 mole) of tetraisobutylthiuram disulfide, M. P. 70.5-71.5 C., with 71 g. (1.0 mole) of chlorine in 30 minutes, employing the same equipment and general procedure as in Example 1, and maintaining the reaction temperature between 65 C. and 75 C. The resulting mixture was allowed to stand at about 50 C. for 3 hours, during which time a large portion of the sulfur formed in the above reaction settled to the bottom of the flask. The diisobutylthiocarbamyl chloride was then decanted from the sulfur. A small sample of this chloride was cooled, yielding a tan solid melting at 4648 C.

A 15% aqueous solution of 1,3,4-thiadiazolyl-2,5-di# sodium mercaptide containing 1.0 mole of the mercaptide was charged into the same apparatus as was used in- Example 1. Stirring was commenced and the above decanted chloride, maintained at about 50 C. in the funnel, was added in 2 hours, while maintaining the temperature of the reaction mixture between 35 C. and 40 C. An aqueous solution of sodium sulfide weighing 326' g, and containing 1.0 mole of the sulfide was added to the mixture, which was stirred for another hour before being filtered. The resulting white solid, l,3,4-thiadiazolyl-2,5- bis(diisobutyldithiocarbamate), was dried at about 50 C., and was found to melt at 106109 C. The product thus obtained weighed 464 g., a yield of 94%.

This product was purified by recrystallization from acetonitrile; white crystalline powder, M. P. 109.5111 C. Calculated for C2oHssN4S5: N, 11:37; S, 32.53. Found: N, 11.37, 11.51; S, 32.4.

EXAMPLE 5 One mole of sym-di-n-butyldicyclohexylthiuram disulfide, M. P. 93-95 C., was converted to N-n-butyl-N-. cyclohexylthiocarbamyl chloride by the general procedure of Example 1. The initial temperature of the reaction mixture was 95 C., but as the reaction progressed the temperature was gradually lowered, being 60 C. at the end of 40 minutes, when 1.0 mole of chlorine had been passed into the mixture. The final mixture was allowed to stand at room temperature for 3 hours, after which it was filtered to separate precipitated sulfur from the above chloride (a dark brown oil).

A 15% aqueous solution of 1,3,4-thiadiazolyl-2,5-disodium mercaptide containing 1.0 mole of this material;

was charged into the equipment :of Example 1. Stirring was commenced and the above filtered chloride, contaming a small amount of dissolved sulfur, was added in 30 minutes; it was not necessary to heat the funnel. During this time the reaction mixture was maintained between 45 C. and 50 C. This mixture, with the product present as an oil, was stirred for 45 minutes more, during which time the oil slowly congealed to a solid mass which became crystalline upon standing overnight. The aqueous solution was decanted from the solid, which was 'thenpulverized, washed well with water, and rinsed with 1500 ml. of methyl alcohol. The resulting solid was slurried with acetone (1 liter), filtered, rinsed with l'liter .of acetone, and dried at 40 C. 1,3,4-thiadiazolyl- 2,5 bis(N n -'butyl N cyclohexyldithiocarbamate) was thus obtained as a tan solid weighing 360 g. and having a melting point of 134-14l C.

This product was purified by dissolving it in benzene at 50 C., filtering, adding an equal volume of hexane, cooling the solution to 10 C., filtering, and rinsing the solid with acetone; this recrystallization was followed by another from an equal-volume mixture of ethyl acetate and acetonitrile. The purified compound obtained in this manner, after being dried at 40 C., was a white powder, M. P. l45146 C. Calculated for Carl-140N455: .N, 10.28. Found: N, 10.20, 10.17.

EXAMPLE 6 A solution of 240 g. (0.75 mole) of dicyclopentamethylenethiuram disulfide (M. P. 129-132 C.) in 500 m1. .of benzene was charged into the chlorination apparatus of Example 1. The solution was stirred while 53.5 ,g. (0.75 .mole) of chlorine was introduced in minutes; the temperature of the reaction mixture was maintained between C. and C. during this period. The mixture was then allowed to stand at about 40 C. for 1 hour, and the benzene solution was decanted from a cake of amorphous sulfur which had been deposited. Benzene was removed by placing the solution under reduced pressure at C. The residue consisted of oil and a small amount of sulfur. This oily cyclopentamethylenethiocarbamyl chloride, after being decanted from the sulfur, weighed 267 g.

This chloride was reacted with a 10% aqueous solution of 1,3,4-thiadiazolyl-2,S-disodium mercaptide conof gummy consistency. The methyl alcohol was' detaining 0.75 mole of the mercaptide, employing the same apparatus and general procedure as in Example 1. .Addition of chloride to mercaptide solution was carried out in 30 minutes (heating of the dropping funnel being unnecessary) (temperature of reaction mixture, 4550 C.), and the mixture was stirred for 30 minutes thereafter. An aqueous solution containing 1.0 mole of sodium sulfide and weighing 326 g. was then added to the mixture, which was stirred for 1 hour more. The resulting slurry was filtered, and the solid product was washed with water, rinsed with 1 liter of methyl alcohol, and dried at C. The product was obtained as a tan powder weighing 138 g. and melting with decomposition at 183185 C.

The solubility of this product in many of the more common solvents was not sufficient to permit recrystallization. However, it was recrystallized from a 1:3 mixture (by volume) of pyridine and dimethyltormamide, filtered oif, rinsed with acetone, and dried at 90 C., a

pure product of melting point 185l86 C. (decomposition) being thus obtained. Calculated for CldHZONSfiZ N, 13.85. Found: N, 13.63, 13.75.

EXAMPLE 7 The disubstituted thiocarbamyl chloride employed in this :example and those employed in the next four examples were prepared by reacting 1 mole of thiophosgene with 2 moles of the appropriate secondary amine, in accordance with the general procedures described many years ago by various chemists such as Billeter, von Braun, and Mazzara.

An aqueouss'olution .(1'5.0;g.)1of -1,3,4thiadiazolyle2$-: disodium :mercaptide containing 0. 15 mole of this ma-' terial was placed .in a l-quart glass vessel provided with thermometer, electrically heated dropping funnel, :and high speed stirrer. Stirring was commenced, and N-. ethyl-N-phenylthiocarbamyl chloride, M. P. :58--59 C. (60 .g., 0.3 mole) was added in molten condition .to thestirred solution in 15 minutes, the temperature of :the reacton mixture being maintainedv between 40 CL :and 45 t Water (400 ml.) was then added .to improve .the fluidity of the mixture, and stirring was continued for an hour.

The :solid product, after being recovered .by. filtration, was washed with water, rinsed with 750 ml. of methyl alcohol, and dried at 40 C. The l,3,4-thiadiazol.yl-'2,-5- bis(N-ethyl-N-phenyldithiocarbamate) thus obtained was an ivory powder weighing 58 g. and melting 165171' 1C.

This product was recrystallized from toluene, recove ered by filtration, rinsed with methyl alcohol, and dried at 40 C. The purified compound was a white crystal-T C. Calculated for line powder, M. P. v179-180 Casi-N455: N, 11.76; S, 33.63. Found: 12.02.; S, 33.6.

EXAMPLE 8 'The'dibcnzylthiocarbamyl chloride used in this experiment was a waxy solid, but it Was easily maintained in liquidcondition by heating it to 60 C. in the dropping funnel.

The apparatus and general procedure of Example "7 were employed to react approximately 0.3'mole of the above chloride with 0.15 mole of l,3,4-thiadiazolyl-2,5- disodiurnmercaptide contained in g. of an aqueous solution. Addition of the chloride was carried out in 15 minutes, the reaction mixture being maintained'between 25 C. and 30 C. This mixture was stirred for 1 hour at about 40 C.

A gummy, plastic mass and an aqueous solution were present, and the latter was decanted. The mass was caused to solidify by chilling it to 10 C., after which it was pulverized. The powder was stirred with 500 ml. of 5% sodium hydroxide solution for 30 minutes at 0" C., filtered off, washed with ice water, and stirred with 1 liter of methyl alcohol at 10 C., and it again became canted and the gummy-mass was dissolved in 250 ml. of hot acetone. The hot solution was filtered to remove a small amount of insoluble material, and the filtrate was diluted with methyl alcohol to the point of turbidity, cooled to 10 C., and more methyl alcohol was added; thetotal amount of alcohol used was 500 ml. The solid which crystallized from the solution was collected by filtration and air-dried. it weighed 25 g. and'melted at 132-139 C. It was 1,3,4-thiadiazolyl-2,5-bis(dibenzyldithiocarbamate) This compound was recrystallized by dissolving it in hot acetone, adding twice the volume of methyl alcohol, and cooling the solution. Filtration and air-drying yielded the compound as an ivory powder, M. P. l39-l4l C. Calculated for CzzHzsNrSs: N, 8.91. Found: N, 8.57, 8.67.

EXAMPLE 9 The di-sec-butylthiocarbamyl chloride used in this experiment was obtained as a gelatinous red solid; 73 g. of this material was dissolved in 100 ml. of acetone for use in the reaction described below.

. Employing the equipment and general procedure of Example 7, the chloride solution (without being heated in the tunnel) was added in 20 minutes to 150 g. of a stirred aqueous solution of 1,3,4-thiadiazolyl-2,5disodium mercaptide which contained 0.15 mole of the latter; the temperature of the reaction mixture was maintained between 35 C. and 40 C. Stirring was continued 1 more hour at the same temperature'conditions.

- The mixture, consisting of an oil and an aqueous solution, was poured into 1 liter of warm water, stirred for 10 minutes, and cooled to 10 C. The oil became a gummy solid, and the aqueous solution was decanted. The solid was washed successively with 500 ml. of 2% sodium hydroxide solution, 500 ml. of 2% hydrochloric acid solution, and 1 liter of warm water.

The solid (red and gummy) was crystallized by dissolving it in hot methyl alcohol, cooling the solution, recovering the solid thereby deposited, washing it with cold methyl alcohol, and air-drying it. This product, 1,3,4-thiadiazolyl-2,5-bis(di sec bntyldithiocarbamate), was tan and crystalline, and melted at 9697 C. Calculated for C2oH3sN4S5: N, 11.37. Found: N, 11.21,

EXAMPLE 10 The di-n-octylthiocarbamyl chloride used in this experiment was a liquid of light reddish color.

The same equipment as used in Example 7 was charged with 125 g. of an aqueous solution of 1,3,4-thiadiazolyl- 2,5-disodium mercaptide which contained 0.125 mole of this material. Stirring was commenced, and approxi mately 0.25 mole of the above chloride (not heated in the funnel) was added rapidly to the solution. The temperature of the reaction mixture was maintained between 35 C. and 45 C. during addition of the chloride and also during 1.5 hours of further stirring.

The reaction product, an oil, was successively washed with water, methyl alcohol, 10% sodium hydroxide solution, hydrochloric acid solution, and water. Finally, it was rinsed with methyl alcohol and dried under reduced pressure. The resulting 1,3,4-thiadiazolyl-2,5- bis(di-n-octyldithiocarbamate) was a liquid weighing 20 g. Calculated for C36H68N4S5; N, 7.82. Found: N, 7.42, 7.30.

EXAMPLE 11 The same apparatus and general procedure were used as in Example 7.

Approximately 0.3 mole of dicyclohexylthiocarbamyl chloride was dissolved in 100 ml. of benzene. This solution (not heated in the funnel) was added rapidly, with stirring, to 50 g. of an aqueous solution of 1,3,4-thiadiazolyl-2,5-disodium mercaptide containing 0.15 mole of the mercaptide. During this addition, the reaction mixture was maintained between 35 C. and 40 C., as well as during an additional 45 minutes of stirring.

The reaction product, a yellow, gummy solid, was removed from the liquid. It was thoroughly leached with 1 liter of methyl alcohol; this treatment converted the gum to a white crystalline solid. The product was successively washed with water, 2% sodium hydroxide solution, and water, and then rinsed with methyl alcohol and dried. The product thus obtained amounted to 70 g. and had a melting point of 179-184 C.

This compound was found to be relatively insoluble in a number of solvents which were tried for purposes of recrystallization. Therefore, it was further purified by leaching it thoroughly with acetone. It was filtered from the acetone, dried at 45 C., and was found to melt at 186188 C. Calculated for Casi-144N485: N, 9.39. Found: N, 9.06, 9.06.

EXAMPLE 12 cipally of 1,3,4-thiadiazolyl-2,5-bis(diethyldithi-ocarbarti ate), was washed with water. The cake was then stirred with dilute sodium hydroxide solution and the resulting slurry was filtered; these operations were repeated several times.

All of the alkaline filtrates were combined, and the solution was acidified with hydrochloric acid; 1,3,4-thiadiazolyl-2-thiol-5-diethyldithiocarbamate was thus precipitated in solid form. In this condition the product was red, but upon recrystallization from methyl alcohol it was obtained as a pale yellow solid which was recovered and dried. This purified product weighed 20 g. and had a melting point of 119.5-120.5 C. Calculated for C'1H11N3Ss1 N, 15.0. Found: N, 16.2.

EXAMPLE l3 Tetrais-opropyl-thiuram disulfide (528 g., 1.5 moles), M. P. ll0-1l3 C., was dissolved in 800 g. of warm "benzene; the solution was charged into a 2-liter, round-bottom fiask fitted with stirrer, thermometer, and gas inlet tube. The solution was stirred vigorously while 106.5 g. (1.5 moles) of chlorine was introduced into it in 45 minutes, the reaction mixture being maintained between 50 C. and 60 C. The mixture comprised diisopropylthiocarbamyl chloride, benzene, and undissolved material;- upon heating the mixture to C., this material dissolved in the liquid. This solution was cooled to room temperature, whereupon sulfur precipitated in crystalline form, 73 g. being removed by filtration. The filtrate was placed under reduced pressure at 60 C. to remove benzene. The residue was diisopropylthiocarbamyl chloride melting at 69-71 C.

The apparatus and general procedure of Example 1 were used to react 359 g. (2.0 moles) of the above chloride with 1.0 mole of l,3,4-thiadiazolyl-2,5-disodium mercaptide contained in 960 g. of aqueous solution. The chloride in molten condition was added to the solution in 1 hour, the temperature of the reaction mixture being maintained between 50 C. and 60 C.

Stirring was continued for 30 minutes after the chloride had been added; 82 g. of an aqueous solution of sodium sulfide containing 0.25 mole of the sulfide was added, and the mixture was stirred for another hour. The resulting slurry was filtered; the solid product was washed with water, filtered, and washed with 1 liter of cold methyl alcohol. The sol-id product was then dried; it weighed 245 g. and melted at 111-1 14 C.

This product was dissolved in 600 ml. of acetonitrile at 75 C., the resulting solution was filtered to remove a small amount of insoluble material, and the filtrate was cooled to 10 C. Crystals came out of solution and Were recovered by filtration; they were rinsed with 500 ml. of cold methyl alcohol and dried at 50 C. 1,3,4- thiadiazolyl-2,5-bis(diisopropyldithiocarbamate) was thus obtained as light tan crystals, weighing 147 g. and melting at ll6-117.5 C.

As a result of our research, a second series of highly useful compounds is made available, namely, the isomers which result from the shifting of the respective N-substituted thiocarbamyl radicals from the side-chain sulfur atoms to the respective nearest nuclear nitrogen atoms in the case of the diesters; in the case of the monomercaptan-monoesters, from the shifting of the hydrogen atom and the N-substituted thiocarbamyl radical from the sidechain sulfur atoms to the respective nearest nuclear nitro gen atoms; and in the case of the monomeroapt-ide-rnonoesters, from the shifting of the N-substituted thiocarbamyl radical from the side-chain sulfur atom to the nearest nuclear nitrogen atoms. The resulting compounds have the and in which Z9. represents one of the group consisting of hydrogen and the radical in s ll in which radical R1 and R2 ave the same meanings as above; 'and in which Zb represents one of the group consisting of the alkali metals and ammonium.

This is illustrated by the following example.

EXAMPLE 14 The acetonitrile filtrate from Example 13 was allowed to stand in an ice bath for 2 hours, a crystalline solid precipitating during this period. This solid was collected by filtration, rinsed with cold methyl alcohol, and dried at 50 C. 3,4-bis(-diisopropyl'thioca-rbarnyl)-l,3,4 thiadiazolidine-2,5-dithione was thus obtained as light greenish-yellow crystals weighing 30 g., and melting at 147-149 C.

The product of Example 13 was analyzed for nitrogen and sulfur with results as follows: N, 12.76, 12.71; S, 36.3. The following analytical results were obtained on the product of Example 14: N, 12.88, 12.81; S, 36.9. Theoretical values for both products are: N, 12.83; S, 36.70. These products are isomers.

The lower melting isomer is relatively insoluble in benzene, hot or cold, while the higher melting isomer is soluble in benzene.

The lower melting of these compounds was isomerized to the higher melting one by maintaining a mixture comprising g. of the compound, M. P. 116-1175 C., and 100 ml. of toluene under reflux (pot temperature, approximately 110 C.) for 12 hours; the solid went into solution soon after the toluene began to reflux. The solution remained clear when it was cooled to room temperatime. However, solid material precipitated when 400 ml. of hexane was added and this mixture was allowed to stand for 2v hours at 10 C. The solid was removed by filtration, rinsed with 200 ml. of cold methyl alcohol, and dried. There was thus obtained 6 g. of ivory powder, M. P. 144.5714! .5 C. This material was dissolved in ml. of hot toluene, and 100 ml. of hexane was added. When this mixture was allowed to stand at 20 C., a solid crystallized out. It was filtered off, rinsed with 50 ml. of methyl alcohol, and dried. The ivory powder weighing 4 g. melted at 147.5149.5 C. A mixed melting point determination with the higher melting compound for which analytical data are given above showed that the two substances were identical.

, Generally speaking, it will be found that the ester compounds usually are lower melting than the corresponding isomers.

Although N-substituted thiocarbamyl chlorides have been employed as reactants in the foregoing exampleswhich illustrate the preparation of the new accelerators,

it is to be understood that other halides may be employed, such as the analogous N-substituted thiocarbamyl bro-- micles and iodides.

The accelerators of this invention are highly effective in accelerating the vulcanization of elastomers which are vulcanizable with sulfur or other vuicanizing agents susceptible to acceleration. Such vulcanizable elastomers include natural rubber, as Well as various synthetic elastomers which are herein considered equivalent to natural rubber. Among synthetic elastomers of this kind there may be mentioned polymers of diolefins, having conjugated olelinic linkages. as well as copolymers of such diolefins with substances polymerizable therewith and having a single olefinic. linkage. Examples, of such synthetic elasto: mers are polyisoprene, polychloroprene, polybutadiene, copolymers of butadiene and styrene such as GR-S, copolyrners of butadiene and acrylonitrile such, as GR-A, butyl rubber, etc.

The new accelerators are highly suitable for use in all. types of rubber compounding, such as in the manufacture of tires, inner tubes, mechanical goods, wire and cable insulation, footwear, drug sundries, cements, dry rubber sponge, etc. Many of them are likewise very suitable for incorporation into water dispersions of the kind employed in latex applications, such as in foam or dipped goods 0P- erations.

The following examples, which are by way of illustration and not of limitation, demonstrate the efiicacy of representative accelerators of the invention.

EXAMPLE 15 The. products of Examples 1, 2, 3, and 6 were tested as accelerators for the vulcanization of GR-S, a butadienestyrene copolymer. The respective accelerators were compounded with this synthetic rubber in accordance with the following formula:

GR-S 100 EPC black Zinc oxide 5- Paraflin softener 5 Sulfur 2 Accelerator 1 The tendency to scorching of two of the uncured compositions was evaluated by means of a Mooney shearing disc viscosirneter operated at 280 F. with the small rotor. The cumulative scorch time, Ts is reported in minutes at which the rise in Mooney units begins to increase at the rate of one unit per minute. Ts was found to be 48 for the compositon containing the accelerator of Example 1, and 83 for the composition containing the accelerator of Example 3.

Samples of the above compositions. were vulcanized by heating in a press for varying periods of time at 307 F. The original physical properties of the vulcanizates were determined, the results being as set forth in Table 1.

Modulus Hardness Mins. cure at." 307 F.

Tensile strength Elongation aeeae 910 720 52 2.020 590 so. 2,320 550 v 62 2,500 am an 120. 4mm (no '50 640 1, 600 560: s"; 1, use 2, 200 s20 62 1,200, 2.400 510 62 1.2811 2,430. 49o: ,es,

13 EXAMPLE 16 The products of Examples 1, 2, 3, and 6 were tested as accelerators for the vulcanization of natural rubber. The respective accelerators were compounded with pale crepe rubber in accordance with the following formula:

Pale crepe 100 Zinc oxide 10 Stearic acid 1 Sulfur 2.5 Accelerator 0.3

Table 2 VULCANIZATE WITH ACCELERATOR F EXAMPLE 1 Mins. cure at 280 F. Modulus Tensile Elonga- Hard- 700% strength tion ness WCAOQN comma beacon ONOIW EXAMPLE 17 The particular compounds employed were the products of Examples 1, 2, 3, 6, 13, and 14, respectively.

The respective accelerators were compounded with synthetic rubber (GR-S, a butadiene-styrene copolymer) according to the following formula:

GR-S 100 EPC black 50 Zinc oxide 5 Coal tar softener 5 Sulfur 2 Accelerator 1 Samples of the compositions thus prepared were vulcanized by heating in a press for varying periods of time at a temperature of 307 F. The original physical properties of the vulcanizates were determined, the results being as set forth in Table 3.

Table 3 VULCANIZATE WITH ACCELERATOR 0]! EXAMPLE 1 Mins. cure at 307 F. Modulus Tensile Elongation Hardness 300% strength VULCANIZATE WITH ACCELERATOR OF EXAMPLE 2 VULCANIZATE WITH ACCELERATOR OF EXAMPLE 3 VULCANIZATE WITH ACCELERATOR OF EXAMPLE 6 VULCANIZATE WITH ACCELERATOR OF EXAMPLE 13 VULCANIZATE WITH ACCELERATOR OF EXAMPLE 14 Examples 15, 16 and 17 demonstrate excellent delayed action characteristics, as well as outstandingly low tendency to scorching. It is to be understood that any other accelerator of this invention may be substituted in these examples with excellent results.

The new accelerators may be employed in proportions other than in those given in the above examples, but ordinarily will be employed in the. range of from 0.1 part to 10 parts per 100 parts of elastomer.

If desired, accelerator activators may be employed with the new accelerators, such as when very quick vulcanization is the aim. The accelerators of this invention may be employed in conjunction with many other types of accelerators, as well as with diverse materials commonly employed in the rubber art, such as antioxidants, softeners, inert materials (e. g., clay and carbon black), zinc oxide, sulfur and other vulcanizing agents, etc. The inclusion of such materials in the new elastomeric composition falls within the purview of the invention.

It is to be understood that the more particular description given above is by way of illustration, and that various modifications are possible and will occur to persons skilled in the art upon becoming familiar herewith. Accordingly, it is intended that the patent shall cover, by suitable expression in the claims, the features of patentable novelty which reside in the invention.

We claim:

1. Rubbery material which has been vulcanized in the presence of from 0.1% to 10% based on the rubbery material of an organic compound having a formula of the group of formulae consisting of:

and

R1 8 R2 in which radical R1 and R2 have the same meanings as above: wherein Zn. represents one of the group consisting of hydrogen and the radical in which radical R1 and Re have the same meanings as above; and wherein Zb represents one of the group consisting of the alkali metals andammonium.

2. A vulcanizate of claim 1 in which the rubbery material is natural rubber.

3. A vulcanizate of claim 1 in which the rubbery material is a vulcanizable synthetic elastomer.

4. A vulcanizate of claim 3 in which the elastomer is a copolymer of butadiene and styrene.

5. Rubbery material vulcanized in the presence of sulfur and of from 0.1% to based on the rubbery material 1,3,4 thiadi'azolyl 2,5 bis(diethyldithiocarbamate).

6. Rubbery material vulcanized in the presence of sulfur and of from 0.1% to 10% based on the rubbery material 1,3,4 thiadiazolyl 2,5 bis(di n butyldithiocarbamate) 7. The process of accelerating the vulcanization of rubbery material which comprises curing the same in the presence of a vuIcanizing agent and of from 0.1% to 10% based on. the rubbery material an organic compound having .a formula of the group of formulae consisting of:

and

Zbr-S 5 8 Rg wherein R1 taken individually represents one of the group consisting of alkyl, aralkyl, aryl, alkaryl, cycloalkyl, alkyl-substituted cycloalkyl, furfuryl, and tetrahydrofurfuryl radicals; wherein R2 takenindividually represents one of the group consisting of alkyl, aralkyl, cycloalkyl, alkyl-substituted cycloalkyl, furfuryl, and tetrahydrofurfuryl radicals; wherein R1 and R2 taken collectively represent one of the group consisting of polymethylene and oxapolymethylene radicals; wherein Z represents one of the group consisting of hydrogen, alkali metals, ammonium, and the radical R1 S N ll- R: V in which radical R1 and R2 have the same meanings as above; wherein 28. represents one of the group consisting of hydrogen and the radical in which radical R1 and Ra have the same meanings as above; and wherein Zn represents one of the group con 10. The method of claim 9 in which the elastomer is a copolymer of butadiene and styrene. V V

11. The method which comprises vulcanizing rubbery material in the presence of a vulcanizing agent and of from 0.1% to 10% based on the rubbery material 1,3,4- thiadiazolyl-2,5-bis (diethyldithiocarbamatel 12. The method which com-prises vulcanizing rubbery material in the presence of a vulcanizing agent and of from 0.1% to 10% based on the rubbery material 1,3,4- thiadiazolyl-LS-bis {di-n-butyldithiocarbamate) l3. Rubbery material vulcanized mine presence of sulfur and of from 0. 1 to 10% based on the rubbery material 1,3,4 thiadiazolyl 2,5-bis(dialkyldithiocarbamate). I 1

14. The method which comprises vulcanizing rubbery material in the presence of a vulcanizing agent and of from 0.1% to 10% based on the rubbery material 1,3,4}

thiadiazolyl-2,5 -b is dialkyldithiocarb amate) Bulifant May 11, 1943 Watt June '12, 1.945 

1. RUBBERY MATERIAL WHICH HAS BEEN VULCANIZED IN THE PRESENCE OF FROM 0.1% TO 10% BASED ON THE RUBBERY MATERIAL OF AN ORGANIC COMPOUND HAVING A FORMULA OF THE GROUP OF FORMULAE CONSISTING OF: 